D-86 distillation curve

A1.1 Results obtained by this test method may be used to calculate the vapor pressure of the gasoline sample, including its Reid vapor pressure (RVP) and to predict the Test Method D 86 distillation curve. 

We apply this method to the feed specified in Table 5.1 using the ASTM D-86 distillation, specific gravity and individual PNA composition. We convert the ASTM D-86 distillation curve to a TBP curve and estimate the molecular weight (using standard API correlations). We then optimize the parameters to match the EP, 90% and 70% of the TBP curve, molecular weight and specific gravity. We compare the calculated and measured values in Figure 5.12 and Table 5.9. 

The flash curve at atmospheric pressure can be estimated using the results of the ASTM D 86 distillation by a correlation proposed by the API. For the same volume fraction distilled one has the following relation ... 

The accuracy of the conversion depends on the smoothness of the D 86 curve. Errors affect essentially the points in the low % distilled ranges. Average error is on the order of 5°C for conversion of a smooth curve. 

The normalized distillation curves, TBP, ASTM D 86, and ASTM D 1160, provide a way to judge the quality of a fractionation performed on petroleum cuts. 

The accuracy depends on the fraction distilled it deviates particularly when determining the initial and final boiling points the average error can exceed 10°C. When calculating the ASTM D 86 curve for gasoline, it is better to use the Edmister (1948) relations. The Riazi and Edmister methods lead to very close results when they are applied to ASTM D 86 calculations for products such as gas oils and kerosene. 

TBP distillations of petroleum fractions at 101.3 kPa (760 torr). The ASTM D 2889 test method, which presents a standard method for calculating EFV curves from the results of an ASTM D 86 test for a petroleum fraction having a 10 to 90 vol % boiling range of less than 55°C (100°F), is also quite useful. 

Figure 11.1 gives typical boiling curves for a light naphtha stream. The curve on the left is a TBP curve and that on the right is an ASTM D-86 curve. The abscissa is volume percent distilled. The ordinate is temperature. Note that the initial and final parts of the curves are quite different because of the fractionation that occurs in the TBP distillation. The 50% boiling point is almost the same (249 and 243 °F). Table 11.1 compares the results of these two methods. 

The simplified fractionator includes a delumper model to convert the 21 kinetic lumps into >80 pure- and pseudo-components, which are then divided into user-specified boiling fractions. A non-linear distribution function generates ideal distillation curves with realistic fraction-to-fraction overlap. The fractionator can inter-convert distillation methods, so a user can calculate D-86, D-1160, D-2887, and/or TBP curves for gasoline and LCO. 

For our convenience, we also add the D-86 stream correlations to every product stream from the column in Figure 2.46. We may also add other types of distillations (TB P, D2887) from the same menu. The simulator arranges the hypothetical and real components in order of increasing boiling point and generates a TBP curve from the cumulative composition and boibng data. Popular correlations... 

Note Distillation curves have been converted to D-86 curves and values marked have been estimated... 

We enter the distillation curve as shown in Figure 2.59. We must enter at least 5 points that include both the initial boiling point and the final point. For this model, we always enter as a 9-point distillation curve. It is also important to make sure that we choose the correct distillation type. As we noted earlier, we corrected all data to follow a D-86 curve. It is possible to use a combination of a D-86, D-1160, SimDist and TBP distillation curves in the assay input. The choice of distillation plays an important role when we create a pseudocomponent list because simulation software converts all distillation curves into a TBP basis. 

We only use routine measurement of feed stock (ASTM D-86, specific gravity, total sulfur and nitrogen content) to build preliminary model. Furthermore, we also use routine measurement of products (compositional analysis of gas products and distillation curve and specific gravity of liquid product) to calibrate the model. Although the resulting model provides good predictions for two months of process and production data, there are several aspects worthy being noticed. 

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